Chromosomal replication in the bacterium Escherichia coli is strictly coordinated to the growth rate of the bacterium. This coordination is controlled through events which regulate the frequency of initiation of each cycle of replication. The long range objective of this proposed research is to understand biochemically how initiation of chromosomal replication occurs, and how it is regulated and coupled to other cellular processes. One approach of the proposed research involves biochemical characterization of mutant forms of dnaA protein to identify the biochemical alterations which make these mutationally altered proteins unable to function in initiation of replication. The second interelated approach involves biochemical characterization of gene products encoded by extragenic suppressors of dnaA mutants in order to understand the mechanism of suppression. These studies will lend insight into the mechanism of initiation of DNA replication, the function of dnaA protein in initiation, and other factors which interact with dnaA protein and contribute to the initiation of replication. A biochemical understanding of the initiation process and its regulation will provide a framework for how these processes may occur in higher organisms, what events may induce the malignant growth of normally quiescent cells, and how these abnormal processes may be controlled or prevented.